In order to cool a semiconductor element such as a central processing unit (CPU) and the like, cooling tools such as heat sinks and heat pipes that are grounded on the semiconductor device are used. Moreover, increases in the amount of generated heat, and increases in the heat-generating area also create problems in high-function devices. A heat transfer path is formed between the ground plane of a cooling tool and a surface of the heat-generating element via a thin-film layer that is created mainly from a high polymer-based material known as a thermal interface material (TIM). Because of this, by fixing these two planes as parallel to each other as possible, efficient and uniform cooling of the element surfaces becomes possible. In actual fact, this type of cooling processing needs to occur in the limited space inside a device, and lop-sided contact and non-uniform temperature distribution arising from individual differences also create problems.
In modern high-function CPUs, there is a tendency for the amount of heat generated by the uptake of a graphic function or an interface function to increase continuously. Because of this, a high-performance cooling mechanism that is able to deal with an increasing amount of generated heat is being sought. Because the element surface area increases if a variety of functions get taken up, the heat transfer surface area increases, and this may be said to be beneficial for the cooling. However, in order to deal with portions where heat is generated in a localized manner, a structure is sought that makes it possible to uniformly cool the entire surface area to a greater extent than is currently the case. For example, in Patent document 1, a structure is described in which the heat sink fins are eliminated, and a direct collisional flow is supplied to the vicinity of the center of an element in which a particularly high cooling performance is required. In this structure, it is possible to supply cool air directly to the vicinity of the area around the center of the element, however, on the other hand, the fins have had to be removed from this area so that a trade-off occurs between this structure and the heat discharge efficiency provided by the fins.
Moreover, for example, in Patent document 2 a structure is proposed in which the pressure generation position of a clip that fixes the heat sink is located in the vicinity of the center of the heat sink. This structure makes it possible to reduce the heat resistance in the area of the TIM. However, the drawback of this structure is that the heat absorption is limited to the surface which is in contact with the element. The role of the distribution of the heat resistance in the TIM area is vital, and the effects thereof are known from the fact that, if the grounding balance is not uniform, then there is a considerable reduction in the heat resistance in areas where an abnormally high pressure is generated. Moreover, areas where an abnormally low pressure is generated are also created, and there is a considerable deterioration in the heat resistance in such areas. Because of this, in Patent document 2 a structure is proposed that, even if the contact balance is no longer equal, maintains a sizable contact pressure in the vicinity of the center of the element. However, the heat absorbing surface area during cooling is limited to the surface area of the element.
Furthermore, for example, in Patent document 3 a cooling structure is proposed that utilizes a cooling pipe. The cooling structure is fixed by a plate spring, and the force from this is generated in the vicinity of the center of the CPU. Because the heat absorption effect is greatest at the surface that is in contact with the heat pipe, the heat pipe is placed in the vicinity of the center of the CPU. The greatest efficiency is achieved by also causing the pressure from the plate spring to be generated in the center, however, in actual fact, because it is not possible to apply pressure to a hollow heat pipe, it is unavoidable for the pressure to be offset from the center by a corresponding amount.